Which Diet's Best? That's Your Choice.

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Is there one diet that's best for losing weight? That's the debate that simmers in weight-loss circles and occasionally boils into a full diet fad. Just recall how the low-carbohydrate craze swept the nation a few years ago.

More recently, the Mediterranean style of eating -- fruit, vegetables, whole grains, fish, yogurt, as well as olive oil and wine -- has caught the fancy of dieters. And with good reason: taste.

Now a number of studies suggest that both the low-carbohydrate approach and the Mediterranean diet can substitute for a traditional low-fat weight-loss diet.

The latest findings come from a two-year Harvard study of 322 moderately obese middle-aged Israelis. Published in last week's New England Journal of Medicine, the study found that "Mediterranean and low-carbohydrate diets may be safe and effective alternatives to low-fat diets." (The study was partly funded by the foundation set up by late diet doctor Robert C. Atkins, a staunch proponent of the low-carbohydrate, high-protein approach.)

But before you add meat and butter to every meal or begin liberally pouring olive oil and wine, know this. "From a weight-loss perspective, it all comes down to calories," says Gary Foster, director of the obesity center at Temple University in Philadelphia.

There are a few other caveats, including the fact that 86 percent of participants in this latest study were men. Lean, fat or somewhere in between, men have more muscle and less fat than women. That makes weight loss a bit easier for those with the XY chromosomes. (Yes, ladies, more proof that life is unfair.)

The study randomly assigned participants -- all employees of a research center in Dimona, Israel -- to a low-fat diet, a low-carb diet or a Mediterranean diet. Participants attended group meetings and met with a dietitian regularly throughout the study. Those who struggled with weight loss received motivational telephone calls from dietitians to help them stay on track. The research center's cafeteria also provided lunches -- (the main meal in Israel) that met their nutritional goals. But participants were free to eat whatever they wanted in the cafeteria.

Daily calorie and fat intake goals were set for those in the low-fat and Mediterranean diet groups. Women were advised to eat 1,500 calories per day; men, 1,800. The low-fat group was counseled to keep total fat to about 30 percent of daily calories; the Mediterranean group, to 35 percent. The low-carb group counted carbohydrate grams rather than calories and was advised to start with just 20 grams per day -- about the amount found in 1 1/2 slices of whole-wheat bread -- for the first two months, with a gradual increase to 120 grams.

As in similar previous studies, the low-carbohydrate group shed pounds the quickest during the first six months of the study. But by about 11 months, the Mediterranean and the low-carb groups were not substantially different in weight loss. Both did better than the low-fat group. At the study's end, those in the low-fat group had lost an average of six pounds; those in the Mediterranean group, nearly eight pounds; and those in the low-carbohydrate group, 10 pounds.

Women did best on the Mediterranean diet, losing about 13 pounds over two years, compared with five pounds for the low-carb diet and just two pounds for the low-fat approach.

"That was a surprise," said Meir Stampfer, a professor at Brigham and Women's Hospital and a co-author of the study. "But there were only 45 women in the study, so don't put too much weight on it because of the small numbers."

Men and women on all three diets significantly whittled their waistlines and improved blood pressure; both changes help cut risk for heart disease and diabetes. But the study found that no one diet was better than another in improving these measures.

Levels of the hunger hormone leptin also improved on all three diets, which means appetite was less likely to be out of control. So did "good" cholesterol, high-density lipoprotein (HDL), and triglycerides, the unhealthy fats that contribute to heart disease. The low-carbohydrate diet produced the biggest improvements for both.

On the other hand, low-density lipoprotein (LDL), a type of "bad" cholesterol, did not change significantly on any of the diets.

"The first take-home message is that if you are embarking on weight loss, start with a low-carbohydrate or Mediterranean diet," Stampfer said. That doesn't mean "eating cheeseburgers and throwing away the bun," he said.

Red meat is less common in Israel than in the United States. Bacon and pork rinds are rarely found. Participants were urged to eat healthy protein, such as fish and chicken without the skin, as well as dairy products. Eating healthy sources of protein low in saturated fat "is one of the key points," Stampfer said.

On all three diets, weight loss took focus and commitment. "You can lose weight," Stampfer said. "But it is hard and it is not going to happen rapidly."

As for sticking with a particular regimen, the low-fat group did best: 90 percent stayed with the plan for two years, followed by 85 percent for the Mediterranean group and 78 percent for the low-carb group.

"You have to choose a diet that you can stick with for the rest of your life," Stampfer said. "Not just to make it to the wedding or for the summer."